The present invention is directed to systems for the injection molding of plastic parts. In particular aspects, the invention is directed to a gating system useful in the molding process for creating optical fiber ferrules.
A fiber optic ferrule is a tubular member that receives the end of an optical fiber or fibers and is then abutted against an opposing ferrule in order to precisely align the fibers so that an optical signal can be transmitted between them. FIGS. 1 and 1A of the drawings depict an exemplary ferrule 10 of a type that is known in the art. As shown there, the ferrule 10 has a generally cylindrical body 12 having ends 14 and 16. The first end 14 has a reduced diameter portion 18 that is adapted to retain a sleeve (not shown) to form an abutting connection with a like ferrule.
The cylindrical body 12 also defines a pair of concentric bores 20 and 22 therewithin. The first bore 20 has a large diameter with an opening 24 at one end of the body 12. The first bore 20 may be slightly tapered along its length. The second bore 22 has a reduced diameter with an opening 26 at the other end of the body 12. The diameter of the second bore 22 is very smallxe2x80x94on the order of 0.02 mm.
Ferrules are typically formed of a polymer or other plastic and are created by injection molding. In order to operate properly, ferrules must be fashioned with great precision. The allowable tolerances for these components are typically only a few microns. Therefore, the details of the molding process must be carefully controlled. Conventional injection molding processes, however, often result in uneven plastic flow patterns and high failure rates. Improved molding processes and systems are desired. Also, even with ferrules that meet specifications, the amount of discarded polymer to usable polymer is high.
The present invention describes devices and methods for the precise molding and creation of ferrules or other plastic parts. In the exemplary embodiment described herein, a molded plastic part is formed that yields four ferrules. The plastic part has a central hub from which four arms extend, each having a ferrule-carrying portion.
A mold is described for molding the plastic part. The mold has a pair of interengageable halves that mate to form a novel series of runners and gates for formation of the plastic part. When molten plastic is injected into the mold, the runners and gates provide for improved plastic flow to form the ferrule-carrying portions of the part. In the described embodiment, molten plastic is flowed from a central chamber through four substantially cylindrical channels. From each channel, the molten plastic then flows into a fan-shaped gate, a ring gate and a parabolic gate. The molten plastic is temporarily accumulated by the gating system and then flowed into a ferrule molding chamber in an evenly distributed manner.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.